1. Field of the Invention
The present invention relates to a backflow preventing mouth plug mounted to a mouth part of a container body, and to a container comprising the backflow preventing mouth plug.
2. Description of the Related Art
A conventional backflow preventing mouth plug is disclosed in Japanese Patent Laid-Open No. 2002-39409. The backflow preventing mouth plug includes a spherical valve and a plug body for receiving the spherical valve. The spherical valve is received in a spherical valve receiving part defined in the plug body. In the backflow preventing mouth cap, a lower sealing portion which contacts the spherical valve to perform a sealing function and an upper sealing portion which seals the spherical valve above the lower sealing portion are formed in the spherical valve receiving part. In using the backflow preventing mouth cap, the spherical valve can be moved between the lower and upper sealing portions.
In the conventional backflow preventing mouth cap, since the spherical valve can be moved in the spherical value receiving part, when the spherical valve is brought into contact with the lower sealing portion to be sealed, a void is created above the spherical valve and fluid may remain in the void. Because this remaining fluid is exposed to oxygen or to saprophytic bacteria that is commonly present in air, the remaining fluid is likely to be oxidized by oxygen or be contaminated by the saprophytic bacteria. Also, due to the fact that no sealing portion is provided while the spherical valve is moved from the upper sealing portion to the lower sealing portion, outside air or saprophytic bacteria may also enter the container.